Average Record Minima...an Unscientific Study.

[March Blizzard]

Yes, i know it's a contradiction of terms! Anyway, ive often wondered about what time of year is the coldest, and consequently, when the lowest mins are most likely to be achieved, so i did a little bit of number crunching to see if any pattern emerged. This was done out of curiosity and was partly motivated by recent talk on NW about how people define/percieve the seasons and the potential for cold. I didn't want to post this in the winter thread as it's a bit long winded. Feel free to use this thread to discuss things like weather singularites and other patterns you may have uncovered.

Basically, I used date records to determine the record minima by date, added them all up, and then divided by the number of entries to get the average temperature of what the record min should be by month. This was done for each month Nov-March. I understand the inherent flaw in this method, and that flaw is that the record min for any given date doesn't necessarily reflect the potential min said date could theoretically acheive, this is evidenced by significantly lower mins on the two dates either side of given date in some cases.

Anyway, the findings, the following list shows the "average record low" by month:

November: -14.5C

December: -20.4C

January: -22.4C

February: -21.8C

March: -16.4C

This suggests that Jan has the lowest average record min, followed by Feb, Dec, Mar, Nov. Not really suprising. The following list shows the average record low by half months. ("a" denotes the first half of the month 1-15, "b" denotes the second half of month 16-30/31. Feb is split into 14/14, the 29th was excluded from the figures.)

Novemeber a: -12.7C

November b: -16.3C

December a: -20.4C

December b: -20.4C

January a: -22.7C

January b: -22.1C

February a: -21.9C

February b: -21.6C

March a: -19.3C

March b: -13.7C

Some interesting results, Dec has nothing between its two halfs, Jan and Feb are fairly consistent but Nov and Mar show a noticeable cooling second half and warming second half, respectively. The March "a" figure demonstrates the potential for extreme cold in the first half of the month. These results roughly agree with the common thought on NW that the best time for extreme cold is from mid Nov to mid March. Before and after these dates extreme cold appears to become increasing unlikely.

The next list shows the "warmest" minima and coldest minima by month, the difference between them, and anomalies. (anomaly demonstrated by the difference between the month's actual record low vs the months average record low):

November; coldest -23.3C (14th), warmest -7.2C (6th), difference: 16.1C.

Record low against month average: -8.8C

Record low against half month average: -10.6C (First half in this case)

December; coldest -27.2C (30th), warmest -14.4C (10th), difference: 12.8C.

Record low against month average: -6.8C. (Same for both month halfs.)

January; coldest -27.2C (10th), warmest -17.2C (1st), difference: 10.0C

Record low aganist month average: -4.8C

Record low against half month average: -4.5C (First half in this case).

February; coldest -27.2C (11th), warmest -18.3C (3 seperate dates), difference: 8.9C.

Record low against month average: -5.4C

Record low against half month average: -5.3C (First half in this case)

March; coldest -22.8C (14th), warmest -9.2C (31st), difference: 13.6C

Record low against month average: -6.4C

Record low against half month average: -3.5C (First half in this case).

A few observations:

1) At -8.8C, November's record low is a huge anomaly compared to the month's average record low, especially when you consider it happend in the first half of the month, which gives an anomaly of -10.6C.

2) November has the biggest difference between it's coldest and warmest mins, at 16.1C.

3) December's record min is more anomalous than March's record min.

4)The record min acheived in January is anomalous by just -4.8C against the month average, -4.5C vs the month half.

5) February is the most consistently cold month, with a difference of just 8.9C between the warmest and coldest mins.

6) At -3.5C, March has the least anomalous record low against the half of month it occured in.

All date records were obtained from Torro's website.

Edited October 18, 2012 by March Blizzard